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The plucky Bushnell brothers invented the military submarine, frightened the mighty British fleet, and gave George Washington a bit of hope.

LEONARDO da Vinci, a great dabbler in military machines, once sketched designs for a crude subma- rine. Yet he refused to publish them, saying he feared “assassination at the bottom of the sea.”

Centuries later, as American colonists stood against the British Empire, a young Yale graduate and his brother set out to realize what Da Vinci feared. Driven by patriotic fervor, David and Ezra Bushnell built the first military submarine, giving a beleaguered George Washington a new weapon against the fearsome British fleet.

More important, the brothers gave military science a preview of modern underwater navigation, mechanical buoyancy, and torpedo weaponry—this despite scarce funds, scorn from military leaders, and the schemes of British spies and competing inventors.

It was 16th-century mathematician William Bourne, an Englishman, who first described in detail how a submersible might be constructed. In the early 1620s, Cornelius Drebbel, a Dutchman living in London, tested Bourne’s ideas. He covered a wooden oval frame with a skin of oiled leather and fashioned oars that poked through tight-fitting flaps. Drebbel took the egg-shaped craft 15 feet beneath the Thames and captured the fancy of King James I, but the English never put the boat to practical use.

Though others tried to perfect a submarine, most were like English wagon maker James Day, who tried to use ballast to make a sailing vessel sink and surface. Day died when his ship failed to surface in a June 1774 demonstration.

The historical record of the lives of the Bushnell brothers is slim. But it’s clear they lived and worked on their family farm in West Saybrook, Connecticut, on Long Island Sound. After their father’s death sometime in the early 1770s, David, who was frail for farming, sold his interest in the land to Ezra and devoted himself to nearly two years of study in preparation for Yale, where he enrolled at 31 and demonstrated a fine mechanical ability.

When the American Revolution erupted in neighboring Massachusetts, the Yale campus became caught up in war. Knowing the colonists lacked the frigates to break the British blockade of the coastline, David Bushnell set out to develop an unconventional weapon—an underwater explosive. Eventually he came up with the idea of using a “watch work” timer to spring a gun flintlock placed inside a waterproof cask of gunpowder. In his second test—witnessed by Connecticut governor Jonathan Trumbull, among other VIPs—two pounds of powder exploded and sent a plume of wood and water “many feet into the air, to the astonishment of spectators,” Bushnell later wrote.

But how could the Americans get the explosive near enough to damage the British fleet? At Yale, David happened upon a particularly intriguing issue of the English Gentleman’s Magazine, which featured scholarly articles about science, among other things. There he found sketches of a boat that could descend below the surface and rise again. Bushnell quickly recognized the possibilities of such a craft as a delivery system for his new weapon.

Returning to his family’s farm after graduating from Yale, David turned for help to his younger brother. Ezra had both building skills and faith in his brother’s intellect. Local artisan Isaac Doolittle crafted the finer mechanical devices based on David’s drawings. All their work and testing was done in secrecy; the British would execute anyone working clandestinely against the Royal Navy.

The result, nicknamed the Turtle, looked like tortoise shells bound together in the shape of an egg. Made of oak reinforced by iron bands, it reached 7.5 feet tall and 6 feet wide and appeared almost entirely black, thanks to layers of pitch and caulk. The pilot entered through an airtight brass top hatch, sat on a stool, and used hand-cranked propellers—a large one in front and a smaller one on top—to maneuver. He steered with a large rudder in back and side protrusions that controlled movement up and down.

The vessel floated naturally. The pilot—typically Ezra Bushnell—submerged by letting water into the craft, then surfaced by pumping it out with a hand pump. Small glass windows in the hatch afforded Ezra a view on the surface. When the Turtle submerged, Ezra used foxfire, the glow from phosphorescent fungi on decaying wood, to read the compass and depth gauge. Two tubes protruding from the brass hatch vented the sub; valves inside the tubes automatically shut when the craft dove below the surface.

Still, the submarine could only stay submerged until its air became stale, a serious limitation. The attack plan had to be simple and fast. The sub would close on its target, then dive and approach from underwater. The pilot would drill into the ship’s hull using an oversize wooden auger screw mounted on the sub’s top with a crank handle inside. A waterproof fuse attached to the auger led to a buoyant wooden gunpowder magazine secured to the submarine’s hull. The magazine was later called a torpedo, after the electric ray Torpedinidae. After releasing the torpedo from the hull, the pilot would propel himself away as the clockwork timer counted down to the explosion.

From a fishing shack on the Connecticut River, the Bushnells tested their submarine, away from prying eyes. It is believed that Ezra nearly died when the ballast pump failed. But once Isaac Doolittle refined that device, the Bushnells had what they believed was a fine new weapon to fight the British.

To sell the new Continental Congress on the idea, the brothers enlisted Dr. Benjamin Gale, a local physician and gold medal winner from the Royal Society of the Arts and Sciences for improvements he made to the drill plow. Gale witnessed a demonstration of the Turtle and asked Benjamin Franklin, an influential member of the society, to arrange funding and approval.

Franklin, not known for being tightlipped, quickly spread news of the invention. Word reached James Brattle, a British informant working as a valet for James Duane, a New York delegate to the Continental Congress. Another would-be inventor, Captain Daniel Joy, a veteran of iron-foundry work, learned enough of the design to propose a craft roughly matching Bushnell’s specifications. Now Bushnell had to be wary of both copycat inventors and the British.

When British vice admiral Molyneux Shuldham received news of the new Yankee threat, he was skeptical. Nevertheless, he put blockading vessels on alert. The new weapon concerned George Washington, commander in chief of the Continental Army; he considered such clandestine work ungentlemanly. The general put questions of honor aside, however, after HMS Phoenix, Rose, and Greyhound landed troops August 22, 1776, at Gravesend Bay on Long Island. Without a navy, Washington could do nothing to prevent the landing. His army, heavily outnumbered, lost the Battle of Long Island days later and soon had to abandon New York City.

On the evening of September 6, 1776, Bushnell’s set out to attack one of the Turtle British ships. (Historians believe the target was the HMS Eagle, the flagship of the Royal Navy fleet at New York.) Ezra Bushnell had come down with camp fever and was replaced by volunteer Ezra Lee, an army sergeant who had only a few days’ training in the sub.

As the staff for Major General Israel Putnam, a top American commander, looked on, the Turtle worked flawlessly and reached the Eagle undetected. Attempts to attach the torpedo were unsuccessful, however, and Lee pulled away without setting his charge. (Some accounts question whether Lee, who would have been breathing carbon dioxide by this time, even reached the Eagle or would have known what he was doing.) After the Turtle surfaced, British lookouts spotted it and launched a longboat to intercept. Lee in turn freed and ignited the torpedo between himself and his pursuers. The explosion didn’t cause any damage.

The Americans later made a second attempt, against HMS Phoenix, with similar disappointing results. Another chase ensued, and Lee apparently was forced to run the sub aground and flee.

Ultimately, the sub was destroyed to keep it out of enemy hands. Though Bushnell was ridiculed for the failed attempts, Washington later called his work “an effort of genius.” The British became so wary of underwater attacks that they moved their ships several miles farther out, weakening their blockade.

Bushnell soon gave them more reason to fear. Refining the timer on his torpedo, he set out to make a floating mine. With this new weapon, Bushnell and a small detachment tried to sink HMS Cerberus, anchored with a captured Yankee schooner. Using a whaleboat, he and the other men placed the mine near their target and escaped undiscovered. Curious seamen on the schooner brought the weapon aboard, and as they examined it, 150 pounds of black powder exploded. The Cerberus survived, but three sailors died and the schooner was destroyed.

Afterward the British arrested Bushnell during a sweep of local waterfront taverns. But the inventor lied about his identity, and his captors failed to recognize the value of their prisoner. General Putnam and Governor Trumbull arranged his release, and upon his return, Bushnell was given a commission in the Continental Army and command of a corps of sappers and miners.

In December 1777, on the Delaware River, he directed an operation that sent a fleet of floating powder kegs downstream to break a British siege. Ice dispersed the kegs, but one exploded and by some accounts sank a boat and killed several sailors.

Bushnell mustered out of the service in 1783 and moved to France, where he may have attempted to sell his designs to European powers. If so, he was not successful. While in Europe, he chanced upon a fellow American inventor, Robert Fulton, who studied his designs. Not long after, in 1800, Fulton built the Nautilus, a submarine, or “plunging boat,” with torpedo. But the American could not persuade the French or the British of the value of his craft—Napoleon considered him a charlatan—and he eventually turned his attention to the steamships that would become his trademark.

David and Ezra Bushnell earned little fame for creating and piloting the first military submarine. Though some accounts suggest Ezra died shortly after his bout with camp fever, family documents suggest he lived until 1786. After his European adventures, David moved to Columbia County, Georgia, where he headed a private school and later worked as physician under the pseudonym “Dr. Bush,” presumably because he was ashamed of the failures of his sub in New York harbor.

He died in 1824, apparently having never married.


Originally published in the Spring 2011 issue of Military History Quarterly. To subscribe, click here